Final answer:
The minimum number of genes affecting the difference in the mean length of corolla tube between two lines of tobacco is 1 gene.
Step-by-step explanation:
The difference in the mean length of the corolla tube between the two lines of tobacco is 6 mm, and the genotypic variance is 1.12 mm2.
To determine the minimum number of genes affecting this trait, we can use the formula:
Number of genes affecting the trait = Genotypic variance / (Difference in the mean length of the trait)^2
Substituting the given values, we get:
Number of genes affecting the trait = 1.12 mm2 / (6 mm)^2
Number of genes affecting the trait ≈ 0.031 genes
Since we can't have a fractional number of genes, the minimum number of genes affecting this trait would be 1 gene. Therefore, the answer is A. 1.